What has been the financial incentive for high tech companies to agree not to recruit from one another?

Fundamentals of human resource management section thinking ethically

1.What has been the financial incentive for high tech companies to agree not to recruit from one another? If the arrangements had not been challenged in court, would you consider them ethical?

2. Given that the justice department has seen these arrangements as possibly violating antitrust laws, what would be the most ethical way to decide whether to recruit employees from other companies?